mybatis分页

川长思鸟来 2022-06-16 11:52 200阅读 0赞

1.把hibernate下的dialect包全部拷贝到mybatis包的jdbc目录下，如下图所示：

2.定义一个ResultSetHandler Interceptor

package cn.machi.utils;

import java.sql.Statement;  
import java.util.Properties;

import org.apache.ibatis.executor.resultset.FastResultSetHandler;  
import org.apache.ibatis.executor.resultset.ResultSetHandler;  
import org.apache.ibatis.plugin.Interceptor;  
import org.apache.ibatis.plugin.Intercepts;  
import org.apache.ibatis.plugin.Invocation;  
import org.apache.ibatis.plugin.Plugin;  
import org.apache.ibatis.plugin.Signature;  
import org.apache.ibatis.session.RowBounds;

@Intercepts( [\{@Signature(type][Signature_type] = ResultSetHandler.class, method = "handleResultSets", args = \{Statement.class\})\})  
public class DiclectResultSetHandlerInterceptor implements Interceptor  
\{  
  
public Object intercept(Invocation invocation) throws Throwable  
\{  
FastResultSetHandler resultSet = (FastResultSetHandler)invocation.getTarget();  
  
RowBounds rowBounds = (RowBounds)ReflectUtil.getFieldValue(resultSet,  
"rowBounds");  
  
if (rowBounds.getLimit() > 0  
&& rowBounds.getLimit() < RowBounds.NO\_ROW\_LIMIT)  
\{  
ReflectUtil.setFieldValue(resultSet, "rowBounds", new RowBounds());  
\}  
return invocation.proceed();  
\}  
  
public Object plugin(Object target)  
\{  
return Plugin.wrap(target, this);  
\}  
  
public void setProperties(Properties properties)  
\{  
\}  
\}

3.定义一个StatementHandler的Interceptor

package cn.machi.utils;

import java.sql.Connection;  
import java.util.Properties;

import org.apache.ibatis.executor.statement.PreparedStatementHandler;  
import org.apache.ibatis.executor.statement.RoutingStatementHandler;  
import org.apache.ibatis.executor.statement.StatementHandler;  
import org.apache.ibatis.jdbc.dialect.OracleDialect;  
import org.apache.ibatis.mapping.BoundSql;  
import org.apache.ibatis.plugin.Interceptor;  
import org.apache.ibatis.plugin.Intercepts;  
import org.apache.ibatis.plugin.Invocation;  
import org.apache.ibatis.plugin.Plugin;  
import org.apache.ibatis.plugin.Signature;  
import org.apache.ibatis.session.RowBounds;

@Intercepts( [\{@Signature(type][Signature_type] = StatementHandler.class, method = "prepare", args = \{Connection.class\})\})  
public class DiclectStatementHandlerInterceptor implements Interceptor  
\{  
  
private static final String DIALECT = "org.apache.ibatis.jdbc.dialect.OracleDialect";  
  
public Object intercept(Invocation invocation) throws Throwable  
\{  
RoutingStatementHandler statement = (RoutingStatementHandler)invocation.getTarget();  
PreparedStatementHandler handler = (PreparedStatementHandler)ReflectUtil.getFieldValue(statement,  
"delegate");  
RowBounds rowBounds = (RowBounds)ReflectUtil.getFieldValue(handler,  
"rowBounds");  
  
if (rowBounds.getLimit() > 0  
&& rowBounds.getLimit() < RowBounds.NO\_ROW\_LIMIT)  
\{  
BoundSql boundSql = statement.getBoundSql();  
String sql = boundSql.getSql();  
  
OracleDialect dialect = (OracleDialect)Class.forName(DIALECT)  
.newInstance();  
sql = dialect.getLimitString(sql,  
rowBounds.getOffset(),  
rowBounds.getLimit());  
  
ReflectUtil.setFieldValue(boundSql, "sql", sql);  
\}  
return invocation.proceed();  
\}  
  
public Object plugin(Object target)  
\{  
return Plugin.wrap(target, this);  
\}  
  
public void setProperties(Properties properties)  
\{  
\}  
\}

4.定义工具类ReflectUtil

package cn.machi.utils;

import java.lang.reflect.Field;  
import java.lang.reflect.InvocationTargetException;  
import java.lang.reflect.Method;  
import java.lang.reflect.Modifier;

import org.apache.log4j.Logger;

public class ReflectUtil  
\{  
private static Logger log = Logger.getLogger(ReflectUtil.class);  
  
private static Object operate(Object obj, String fieldName,  
Object fieldVal, String type)  
\{  
Object ret = null;  
try  
\{  
// 获得对象类型  
Class<? extends Object> classType = obj.getClass();  
// 获得对象的所有属性  
Field fields\[\] = classType.getDeclaredFields();  
for (int i = 0; i < fields.length; i++)  
\{  
Field field = fields\[i\];  
if (field.getName().equals(fieldName))  
\{  
  
String firstLetter = fieldName.substring(0, 1)  
.toUpperCase(); // 获得和属性对应的getXXX()方法的名字  
if ("set".equals(type))  
\{  
String setMethodName = "set" + firstLetter  
\+ fieldName.substring(1); // 获得和属性对应的getXXX()方法  
Method setMethod = classType.getMethod(setMethodName,  
new Class\[\] \{field.getType()\}); // 调用原对象的getXXX()方法  
ret = setMethod.invoke(obj, new Object\[\] \{fieldVal\});  
\}  
if ("get".equals(type))  
\{  
String getMethodName = "get" + firstLetter  
\+ fieldName.substring(1); // 获得和属性对应的setXXX()方法的名字  
Method getMethod = classType.getMethod(getMethodName,  
new Class\[\] \{\});  
ret = getMethod.invoke(obj, new Object\[\] \{\});  
\}  
return ret;  
\}  
\}  
\}  
catch (Exception e)  
\{  
log.warn("reflect error:" + fieldName, e);  
\}  
return ret;  
\}  
  
public static Object getVal(Object obj, String fieldName)  
\{  
return operate(obj, fieldName, null, "get");  
\}  
  
public static void setVal(Object obj, String fieldName, Object fieldVal)  
\{  
operate(obj, fieldName, fieldVal, "set");  
\}  
  
  
private static Method getDeclaredMethod(Object object, String methodName,  
Class<?>\[\] parameterTypes)  
\{  
for (Class<?> superClass = object.getClass(); superClass != Object.class; superClass = superClass.getSuperclass())  
\{  
try  
\{  
//superClass.getMethod(methodName, parameterTypes);  
return superClass.getDeclaredMethod(methodName, parameterTypes);  
\}  
catch (NoSuchMethodException e)  
\{  
//Method 不在当前类定义, 继续向上转型  
\}  
\}  
  
return null;  
\}  
  
  
private static void makeAccessible(Field field)  
\{  
if (!Modifier.isPublic(field.getModifiers()))  
\{  
field.setAccessible(true);  
\}  
\}  
  
  
private static Field getDeclaredField(Object object, String filedName)  
\{  
for (Class<?> superClass = object.getClass(); superClass != Object.class; superClass = superClass.getSuperclass())  
\{  
try  
\{  
return superClass.getDeclaredField(filedName);  
\}  
catch (NoSuchFieldException e)  
\{  
//Field 不在当前类定义, 继续向上转型  
\}  
\}  
return null;  
\}  
  
  
public static Object invokeMethod(Object object, String methodName,  
Class<?>\[\] parameterTypes, Object\[\] parameters)  
throws InvocationTargetException  
\{  
Method method = getDeclaredMethod(object, methodName, parameterTypes);  
  
if (method == null)  
\{  
throw new IllegalArgumentException("Could not find method \["  
\+ methodName + "\] on target \[" + object + "\]");  
\}  
  
method.setAccessible(true);  
  
try  
\{  
return method.invoke(object, parameters);  
\}  
catch (IllegalAccessException e)  
\{  
  
\}  
  
return null;  
\}  
  
  
public static void setFieldValue(Object object, String fieldName,  
Object value)  
\{  
Field field = getDeclaredField(object, fieldName);  
  
if (field == null)  
throw new IllegalArgumentException("Could not find field \["  
\+ fieldName + "\] on target \[" + object + "\]");  
  
makeAccessible(field);  
  
try  
\{  
field.set(object, value);  
\}  
catch (IllegalAccessException e)  
\{  
e.printStackTrace();  
\}  
\}  
  
  
public static Object getFieldValue(Object object, String fieldName)  
\{  
Field field = getDeclaredField(object, fieldName);  
if (field == null)  
throw new IllegalArgumentException("Could not find field \["  
\+ fieldName + "\] on target \[" + object + "\]");  
  
makeAccessible(field);  
  
Object result = null;  
try  
\{  
result = field.get(object);  
\}  
catch (IllegalAccessException e)  
\{  
e.printStackTrace();  
\}  
  
return result;  
\}  
  
\}

5.更新mapper configuration文件，添加如下几条，注意plugins在整个configuration文件中的顺序

6.使用方法同mybatis逻辑分页，拦截器会自动拦截执行SQL的地方，加上分页代码：

getSqlSession().selectList(mapId, queryKey,new RowBounds(pageId, pageSize));

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